JP5320897B2 - Detection device of ground fault in DC equipment - Google Patents

Description

  The present invention relates to ground fault detection of a DC device in a substation in a feeding system of a DC electric railway.

  First, an example of a ground fault in a DC electric railway substation (hereinafter referred to as a substation) will be described with reference to FIG. FIG. 2 shows a feeder system, including a rectifier transformer 101, a rectifier 102, DC high-speed circuit breakers (HSCB) 103a (54P), 103b (54F), 103c (54F), and a DC ground fault overvoltage relay 106 ( 64P) is located in the substation. Also, the AC high voltage transmitted from the power plant is stepped down by the rectifier transformer 101, and the stepped-down AC voltage is converted into a DC voltage by the rectifier 102, and is passed through the DC high speed circuit breakers 103a and 103c. Electric power is transmitted to the electric wire 104 and a predetermined voltage is applied to the electric vehicle 107. The DC ground fault overvoltage relay 106 is for detecting a voltage caused by the ground fault.

  Here, the DC high speed circuit breaker 103a is for the rectifier 102, and the DC high speed circuit breakers 103b and 103c are for the feeder line. The DC high-speed circuit breaker 103b is connected to the feeders in other sections, but is not shown.

  The DC high-speed circuit breaker, one of the equipment used in this substation, has many moving parts, an arc is generated due to current interruption, and it may cause a ground fault due to the arc, and a small current interruption may not be possible. This often causes ground faults in substations.

  In FIG. 2, when a ground fault occurs on the primary side of the DC high speed circuit breaker 103c, the circuit of the rectifier 102 → DC high speed circuit breaker 103a → ground fault → ground resistance → rail 105 → rectifier 102 is connected to the ground fault current. Flows. Moreover, the value of this grounding resistance is the value of the substation A class grounding resistance, and is generally 5Ω or less. For this reason, in a general 1500V feeding system, the ground fault current is about 1500V / 5Ω = 300A. Since the overcurrent detection of the DC high speed circuit breaker 103a and the failure selection relay is several thousand A, the above current may not be detected.

  The setting of the overcurrent protection of the DC high speed circuit breaker 103a is determined by the capacity of the rectifier 102. When the capacity of the rectifier 102 is 3000 kW, the setting of the DC high speed circuit breaker 103a is generally 6000A.

  For this reason, the ground fault accident detection in the substation employ | adopts the overvoltage detection system which detects the voltage between a rail and the earth using a DC ground fault overvoltage relay (64P).

Problems with this overvoltage detection method will be described with reference to FIG. 2 and FIG. 3 which is an equivalent circuit in the event of a ground fault in FIG.
<1. If the ground fault point resistance is large, the DC ground fault overvoltage relay may not be able to detect the voltage>
This will be described with reference to FIG. The voltage detected by the DC ground fault overvoltage relay 106 is determined by the class A grounding resistor 111 and the ground fault current Is in the substation. In general, in a 1500V feeding system, the DC ground fault overvoltage relay is set to 500V. Now, if a high-resistance ground fault occurs, the ground fault point resistance 110 is 20Ω, and the class A grounding resistor 111 is 5Ω, the ground fault current Is = 1500 / (5 + 20) = 60 A, the detection voltage of the DC ground fault overvoltage relay 106 = 5 × 60 = 300V, and the DC ground fault overvoltage relay 106 does not operate.
<2. When a ground fault occurs, it may not be possible to distinguish between substation and off-site>
In the overvoltage detection method, if an accident outside the substation premises, the feeder circuit breaker selectively cuts off the power to the affected load, and the fault inside the substation premises detects a ground fault overvoltage relay signal. The substation is stopped based on However, even if an accident occurs outside the substation, the DC ground fault overvoltage relay may operate and the substation may stop. This will be described with reference to FIG.

  In FIG. 2, when a ground fault occurs on the outer line side (the DC high speed circuit breaker 103 c side of the electric wire 104), the class A grounding resistance in FIG. 3 is a resistance between the rail and the ground. In this case, since the ground fault current is large, it is necessary to detect the accident with the overcurrent flowing through the DC high-speed circuit breaker 103c, and to shut off the DC high-speed circuit breaker 103c. Since the relay 106 detects the voltage, the DC ground fault overvoltage relay 106 is also operated depending on the situation. Therefore, if the DC ground fault overvoltage relay 106 is also operated at the time of an accident outside the substation, it becomes impossible to distinguish whether the ground fault occurs at the substation or off-site.

  For example, Patent Document 1 discloses a method of detecting a ground fault by detecting overcurrent in contrast to such a problematic overvoltage detection method.

  FIG. 4 shows a conventional general HSCB structure. The thing of FIG. 4 is the switchboard 1, its front door 2 and back door 3, DC high-speed circuit breaker 4, drawer device 5, grounding conductor 6, grounding metal fitting 7, drawer device mounting bolt 8, grounding bar 9, switchboard grounding wire 10 and a dedicated wiring 11 are provided.

  The switchboard 1 is disposed on the ground and includes a front door 2 and a back door 3 and houses a DC high-speed circuit breaker 4 and a DC disconnector (not shown).

  The DC high-speed circuit breaker 4 interrupts the ground fault current at high speed when the main circuit is grounded. For example, since the holding power source is not required, the capacity of the DC power source can be reduced. A machine-holding type having characteristics such as not changing is used. Usually, the breaking current is several thousand A. Note that the current flowing through the DC high-speed circuit breaker 4 flows to the main circuit conductor including the feeder 104 in FIG. 2, for example.

  The drawing device 5 is a device for performing insertion / drawing operation of the drawer type DC high-speed circuit breaker 4 to be housed, and is conductive.

  The ground conductor 6 is provided on the upper surface of the pedestal of the drawing device 5 and comes into contact with the ground metal fitting 7.

  The grounding metal 7 is attached to the outer casing of the DC high speed circuit breaker 4 and comes into contact with the grounding conductor 6.

  The drawing device mounting bolt 8 is for fixing the switchboard 1 and the drawing device 5 installed on the ground.

  One end of the ground bar 9 is in contact with the ground, and is for grounding a device connected to the other end.

  The switchboard ground line 10 is for connecting the switchboard 1 and the ground bar 9 to ground the switchboard 1.

  The dedicated wiring 11 connects the ground conductor 6 and the ground bar 9 and grounds the DC high-speed circuit breaker 4 (HSCB main body) via the ground conductor 6 and the ground fitting 7. However, in the thing of FIG. 4, it is not necessarily attached.

In this way, the grounding metal fitting 7 is attached to the outer casing of the DC high-speed circuit breaker 4, and this grounding metal fitting 7 comes into contact with the ground conductor 6 provided in the conductive drawing device 5, and the drawing device 5 is drawn out. The outer casing of the DC high speed circuit breaker 4 is grounded by being fixed to the switchboard 1 by the device mounting bolts 8 and via the switchboard grounding wire 10 (or the dedicated wiring 11) and the grounding bar 9.
JP 2004-194471 A (paragraphs [0017] to [0020], FIG. 4 and the like).

  As described in the third embodiment, in Patent Document 1, each circuit breaker is also electrically separated by electrically separating the casing in circuit breaker units. A ground wire is individually laid for each housing, and a ground fault current flowing in the ground wire is detected for each electrically separated circuit breaker.

  However, the ground fault current flows through various paths between the frame and the ground, such as a path from the anchor bolt to the ground, in addition to flowing to the ground line for each breaker. Therefore, it is necessary to reduce the current flowing through the ground line and to reduce the settling value of the current detector.

  The present invention has been made based on the above problems, and provides a detection device for a ground fault in a DC device in which a ground fault is reliably detected and a reliable ground fault can be detected even at the time of a high resistance ground fault. It is to provide.

In order to solve the above problems, the present invention provides a grounded casing, a DC high-speed circuit breaker for a DC circuit that is disposed in the casing so as to be insulated from the casing, and has an outer casing. A grounding line connecting the outer casing of the DC high-speed circuit breaker and the ground, and current detection means for detecting a ground fault current flowing through the grounding line are provided.

The DC high-speed circuit breaker is insulated from the housing through an insulator.

  Further, the ground line is composed of only one ground line.

According to the above configuration, since the ground fault current does not flow except the ground line by detecting the ground fault current flowing through the ground line from the outer casing of the DC high speed circuit breaker insulated from the casing, Detection is performed reliably, and reliable ground fault detection is possible even in the case of a high resistance ground fault, and no malfunction occurs due to an accident outside the substation.

In addition, since the ground fault current does not flow except for the ground line on either the primary side or the secondary side, the ground fault is reliably detected.

According to the first to third aspects of the present invention, the ground fault current does not flow except the ground line by detecting the ground fault current flowing through the ground line from the outer casing of the DC high speed circuit breaker insulated from the casing. Therefore, the ground fault is reliably detected, and the ground fault can be reliably detected even in the case of a high resistance ground fault, so that no malfunction is caused by an accident outside the substation. In addition, it is not affected by the ground fault and no malfunction occurs.

In addition, since the ground fault current does not flow except for the ground line on either the primary side or the secondary side, the ground fault is reliably detected.

  Hereinafter, a ground fault detection device for a DC device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram according to an embodiment of the present invention. The same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted. 4 differs from that of FIG. 4 in that an insulator 12 is provided between the switchboard 1 and the drawing device 5 and that the drawing device mounting insulating bolt 13 replaces the drawing device mounting bolt 8 so that the drawing device 5 and The insulator 12 is fixed to the switchboard 1, the outer casing of the DC high speed circuit breaker 4 is grounded only by the dedicated ground wire 21, and the ground fault current detection CT 14 is connected to the dedicated ground wire 21. It is provided.

  Here, the insulator 12 has substantially the same shape as the bottom surface portion of the drawing device 5 and is in contact with the switchboard 1 and the drawing device 5, but is not necessarily the same shape as the bottom surface portion of the drawing device 5. Need not be. The insulator 12 is formed of a synthetic resin such as an epoxy resin.

  As the drawing device mounting insulating bolt 13, a bolt coated with a synthetic resin such as an epoxy resin is used.

  The ground fault current detection CT 14 is provided on the dedicated ground line 21, and normally no current flows through the dedicated ground line 21, so the detected current is zero current, but when a ground fault occurs, the dedicated ground line When a ground fault current flows through the wire 21, the current is detected and the occurrence of a ground fault is detected.

  The dedicated ground line 21 is dedicated to the DC high-speed circuit breaker 4 and is preferably composed of only one.

  In this way, the outer casing of the DC high-speed circuit breaker 4 is isolated from the switchboard 1 by the electrically connected drawing device 5 and grounded only by the dedicated grounding wire 21, so that the ground fault current varies. Only the dedicated ground line 21 flows without flowing through the route. Therefore, the ground fault current can be reliably detected by the ground fault current detection CT 14. In addition, reliable ground fault detection is possible even in the case of a high resistance ground fault, and no malfunction occurs due to an accident outside the substation.

  That is, when an off-ground ground fault or a ground fault occurs at an adjacent substation, the ground fault current flows from the point of the accident through the ground to the dedicated ground line of the HSCB of the present invention. Since the directions are opposite, the detection current of the ground fault current detection CT 14 is in the reverse direction, and the HSCB does not malfunction. Therefore, it is not affected by an off-ground ground fault and does not cause a malfunction.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

  For example, it is possible to insulate the entire distribution board 1 of FIG. 1 from the ground, and provide a dedicated ground line 21 on the distribution board 1 to detect the current of the dedicated ground line 21.

  For example, instead of disposing the insulator 12 in FIG. 1 between the switchboard 1 and the drawer device 5, the DC high-speed circuit breaker 4 is connected to the switchboard 1 by covering the drawer device 5 itself with a predetermined insulating material. It may be insulated.

  In the embodiment of the present invention, a DC high-speed circuit breaker is used as a DC device, but the present invention is not limited to this, and it can be applied to other DC devices such as a silicon rectifier and an inverter. Is possible. Even in that case, the same operations and effects as the above-described embodiment are achieved.

The block diagram of the detection apparatus of the ground fault in the DC high-speed circuit breaker (HSCB) of this Embodiment. Schematic of the overvoltage detection at the time of the primary ground fault in a DC feeding circuit. The equivalent circuit figure at the time of the ground fault accident in FIG. The block diagram which shows the attachment condition of the conventional DC high-speed circuit breaker (HSCB).

Explanation of symbols

1 ... switchboard (frame)
2 ... Front door 3 ... Back door 4,103a-103c ... DC high speed circuit breaker (DC equipment)
DESCRIPTION OF SYMBOLS 5 ... Leading device 6 ... Grounding conductor 7 ... Grounding metal fitting 8 ... Leading device mounting bolt 9 ... Grounding bar 10 ... Switchboard grounding wire 11 ... Dedicated wiring 12 ... Insulator 13 ... Leading device mounting insulating bolt 14 ... CT for ground fault current detection (Current detection means)
21 ... Dedicated grounding wire 101 ... Rectifier transformer 102 ... Rectifier 104 ... Feed wire 105 ... Rail 106 ... DC ground fault overvoltage relay 107 ... Electric car 110 ... Ground fault resistance 111 ... Class A grounding resistance

Claims (3)

A grounded enclosure,
A DC high-speed circuit breaker for a DC circuit disposed in the housing so as to be insulated from the housing, and having an outer sheath;
A grounding wire connecting the outer casing of the DC high-speed circuit breaker and the ground,
An apparatus for detecting a ground fault in a DC device, comprising: a current detection unit configured to detect a ground fault current flowing through the ground line. 2. The apparatus for detecting a ground fault in a DC device according to claim 1, wherein the DC high-speed circuit breaker is insulated from the housing through an insulator.   The said grounding wire consists of only one grounding wire, The detection apparatus of the ground fault in DC apparatus of Claim 1 or 2 characterized by the above-mentioned.

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